Netflix rates your Internet provider on performance

Netflix may have started out sending you DVDs via snailmail, but the company’s future lies in streaming TV shows and movies over the Internet. It recently began offering a streaming-only service option in the U.S., and Netflix traffic already accounts for about 20 percent of Net traffic during prime time.

So it would make sense that the company pays attention to the quality of the connections that Internet service providers offer to their customers. In a blog post, Netflix Director of Content Delivery Ken Florance posted a chart showing which of the biggest U.S. ISPs offer the most robust connections to their subscribers. It’s based on how well the providers can deliver Netflix’s HD movies to customers.

Now, that chart is a bit confusing (you can click on it to see a bigger view), but CNet has parsed its squiggles and produced the following ranked list:

Houstonians, take note: Comcast is ranked as the second-best provider for Netflix content, behind another cable provider, Charter. Time Warner Cable comes in third.

(Irony alert: Comcast is involved in a dispute with Level 3 Communications, one of the providers of bandwidth to Netflix, over how much it should be paying Comcast for its connection to the cable company.)

This makes sense because, traditionally, cable providers have offered much faster connections than telephone companies, which rely on DSL. Advances in DSL have made the telcos faster, but overall they still lag behind cable. Thus, Verizon, AT&T and BellSouth are all in the middle of the pack.

As any customer of Netflix knows, you don’t always get the fastest connection – and thus the best video quality – every time. For example, on my Roku device, I’ll occasionally see Netflix’s quality step back a notch, even though I have a 16-megabit-per-second connection to Comcast. Still, the Netflix data reflects averages over time. Florance provides some technical details:

Currently, our top HD streams are about 4800 kilobits per second. Clients may switch through a number of bitrates as they ramp up to the highest stream, or shift down from the highest stream if they cannot sustain play at that rate due to throughput constraints. No client would sustain a 4800 stream from start to finish (there would at least be a few smaller streams averaged in for startup) but the higher the sustained average, the greater the throughput the client can achieve, and the greater the image quality over the duration of the play. As we use a number of CDNs, and our clients can adapt to changing network conditions by selecting the network path that’s currently giving them the best throughput, Netflix streaming performance ends up being an interesting way to measure sustained throughput available from a given ISP over time, and therefore the quality of Netflix streaming that ISP is providing to our subscribers. Obviously, this can vary by network technology (e.g. DSL, Cable), region, etc., but it’s a great high-level view of Netflix performance across a large number of individual streaming sessions.

Netflix plans to update this data monthly. It will be interesting to see if customers seeking better streaming video connections use it to help make decisions about switching ISPs. I know this: The numbers make me happier that I’m a Comcast customer.